fix: Allow merging a RegExp to itself

Closes #145.

Author: bebraw

CHANGELOG.md

@@ -1,5 +1,9 @@
 # Changelog
 
+## 5.1.3 / 2020-08-30
+
+- Fix - Allow merging a `RegExp` to itself #145
+
 ## 5.1.2 / 2020-08-18
 
 - Fix - Allow overriding an object field with `null` #144

src/join-arrays.ts

@@ -19,12 +19,17 @@ export default function joinArrays({
     if (isFunction(a) && isFunction(b)) {
       return (...args: any[]) => _joinArrays(a(...args), b(...args), k);
     }
+
     if (isArray(a) && isArray(b)) {
       const customResult = customizeArray && customizeArray(a, b, newKey);
 
       return customResult || [...a, ...b];
     }
 
+    if (isRegex(b)) {
+      return b;
+    }
+
     if (isPlainObject(a) && isPlainObject(b)) {
       const customResult = customizeObject && customizeObject(a, b, newKey);
 
@@ -53,6 +58,10 @@ export default function joinArrays({
   };
 }
 
+function isRegex(o) {
+  return o instanceof RegExp;
+}
+
 // https://stackoverflow.com/a/7356528/228885
 function isFunction(functionToCheck) {
   return (

test/merge.test.ts

@@ -41,6 +41,32 @@ function normalMergeTest(merge, loadersKey) {
     );
   });
 
+  it("should allow merging optimization config to itself (#145)", function () {
+    const config = {
+      optimization: {
+        runtimeChunk: {
+          name: "runtime",
+        },
+
+        splitChunks: {
+          minChunks: 2,
+          minSize: 30000,
+
+          cacheGroups: {
+            clientApplication: {
+              name: "clientApplication",
+              test: /applications\/client/,
+              chunks: "all",
+              enforce: true,
+            },
+          },
+        },
+      },
+    };
+
+    assert.deepEqual(merge(config, config), config);
+  });
+
   it("should error on promise", function () {
     const a = {
       module: {},